Various industrial applications require traction cables. Often, network cables such as electric or optical cables are pulled into place in a tunnel by first passing a metal cable through the tunnel, attaching the metal cable to the network cable, and the network cable is pulled into position by retracting the metal cable. For illustrative purposes, a typical industrial application can have a cable traction capacity of 25 000 lbs, 50 000 lbs, or even more, for instance. Depending on the application, the length of the cable can vary.
It was known to handle cable by loading the cable on a large drum mounted to rotate about a horizontal axis. The drum was driven by a hydraulic actuator which exerted a rotary force on the axle of the drum. Similar to the operation of a common winch, the cable was to be unloaded from the drum by manual force traction the free end thereof. Once attached to that which required traction, the cable is reeled in by the hydraulically actuated drum. In such systems, the drum serves both as means to accumulate the cable and means to pull the cable.
Such known systems were satisfactory to a certain degree, but there remained room for improvement. For instance, there was a challenge in adapting the traction force exerted on the drum both because the force exerted on the cable depended on the amount of cable present on the drum (i.e. for a given rotary force exerted on the axis, the cable force diminishes as the leverage arm separating it from the axis increases), and because it was difficult to obtain an indication of the actual traction force exerted at any given time. Further, the cable reeled on the drum tended to exert twisting forces which strongly affected the ability of forming a regular spiral configuration on the drum and sometimes caused the cable to become jammed. In an attempt to compensate for some of these drawbacks, it was often required that an operator hold a portion of the cable during rotation of the drum, which was undesirable.